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Use AO as Tx to Remote indicator ( loop powered type)

Created by: Ansigiangho at: 5/20/2011 7:29 AM (12 Replies)

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5/20/2011 7:29 AM	Rate (0)
Ansigiangho Posts: 7 Rating: (0)	Dear Expert We have a remote indicator powered by loop power 4-20mA. So can we use AO card as transmitter for remote indicator? Voltage drop on it is max 1.1V. Thanks in advance for your support.
Ansigiangho Posts: 7 Rating: (0)
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5/20/2011 2:37 PM	Rate (0)
H-H Platinum Member Joined: 7/2/2008 Last visit: 9/30/2024 Posts: 928 Rating: (308)	Hello Ansigiangho, Yes you can use the AO as long as the input impedance of the indicator is suitable for the AO module. Best regards. H-H

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5/21/2011 4:11 AM	Rate (0)
Ansigiangho Posts: 7 Rating: (0)	Thank you. Because of voltage drop Max 1.1V, I think input indicator impedance is about 275 Ohm. It is okie? Siemes AO card can power for that one?
Ansigiangho Posts: 7 Rating: (0)
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5/21/2011 9:07 AM	Rate (0)
IBN-Service Posts: 8946 Rating: (999)	R = U / I R = 1.1V / 0.02A R = 55 Ohm That is OK for SIMATIC 4..20 mA analoge output cards. Usually, they will work up to 500 Ohm.
IBN-Service Posts: 8946 Rating: (999)
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This contribution was helpful to 1 thankful Users H-H

5/23/2011 9:22 AM	Rate (0)
Ansigiangho Posts: 7 Rating: (0)	Thank you I would like to send to you schematic drawing, include specification of indicator. I hope it is useful for your understanding about my concern: Power loop can work without extenal power supply? Attachment Loop wiring for indicator1.JPG (376 Downloads)
Ansigiangho Posts: 7 Rating: (0)
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5/23/2011 9:36 AM	Rate (0)
Ansigiangho Posts: 7 Rating: (0)	Dear Experts I attach specification of indicator for you. I just want to make sure that Siemens's AO module can used for powering to that indicator. Thanks in advance. Attachment P&F 130039_eng.pdf (397 Downloads)
Ansigiangho Posts: 7 Rating: (0)
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5/24/2011 6:19 AM	Rate (0)
Ansigiangho Posts: 7 Rating: (0)	Dear Friends. Any help. I need it so mucn Thank you.
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5/24/2011 6:48 AM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 10/7/2024 Posts: 10229 Rating: (1181)	Hello, "Loop powered" - means in the same 2 wire you send 24 V DC and 4-20mA. By 2-wire it means the transmitter is powered form the system to which it is connected... normally 24VDC and 4-20mA signal is connected to the control system using only one single pair of wires, by 4-wire it means the transmitter is powered from a external power supply and signal 4-20mA which is a separate pair of wires is connected to the system, e.g. a mag flow meter is powered 24VDC or 110VAC or 230VAC and output 4-20mA is connected to DCS/PLC AI board channel. What does it mean in your case? Main application of the DA4/Ex40 is to display a measured variable or control signal in a hazardous process area. The zero and span of the display are independently adjustable so that the indicator can easily be calibrated on site to display any linear or square signal such as temperature, flow or pressure. Let's say your sensor gives 4-20mA signal and you should measure it. You will need AI card which read 4-20mA and gives power suply to this sensor. In series (using the same wires) with this sensor you can connect DA4/Ex40. And that's it. Best regards, Hristo MIhalev

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5/24/2011 7:33 AM	Rate (0)
Ansigiangho Posts: 7 Rating: (0)	Thank you,Hristo MIhalev I got your comment. It is a common application. I think this indicator can work with AI card as signal receiver and as power supply to that one. But, my concern is different. I dont know I can connect from Siemens's AO module to that indicator without external power supply or not?
Ansigiangho Posts: 7 Rating: (0)
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5/24/2011 7:40 AM	Rate (0)
UMENCHO Diamond Member Joined: 3/21/2006 Last visit: 10/7/2024 Posts: 10229 Rating: (1181)	According to the calculation you can. Unfortunately for the moment only you could confirm if this way works... Best regards, Hristo Mihalev

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